IATSE Local 311 was chartered in Middletown, NY on March 27, 1922 by Robert Doolittle, Charles Doolittle, Harry Hall, Joseph Carpenter, Robert Wittock, George McCarter, John Yeager and Eugene McMullen. The 8 founding members were motivated to organize when the theaters of Middletown became consolidated under a single owner - Benjamin Lefkowitz. The monopolization, however, worked to the employees' advantage, as the owner could not ignore the strength of the demands of all of his theaters' technicians at once. At the time, Middletown was a industrial hub on the railroads, and served as an entertainment destination for those who lived locally and those who passed through town. Union members served as stagehands and craftsmen, and as projectionists for "moving pictures" as well. In addition to The Stratton and The Show Shop, the largest of Middletown's theaters was The New State Theater, which opened in 1921 and held over 1,400 seats. The Paramount, which opened in the 1930's, held the honor of screening the first sound motion picture in Middletown - "Showboat."

In nearby Newburgh, IATSE Local 45 had already been established since 1896. The Newburgh charter was only three years younger than the formation of the union itself. At the time, the union was still known as "The National Alliance of Theatrical Stage Employees," and would not become the International Alliance of Theatrical Employees (IATSE) until 1902. The formation of the theatrical union was part of the great labor movement of the 19th Century, as workers across all trades demanded fair pay, safe working conditions and an end to child labor. Newburgh theaters such as The Ritz could seat over 1,400 guests, and they became frequent tour stops for famous artists and celebrities on their ways to and from New York City. The Academy, Cameo, Park and Broadway Theaters were established near one-another in downtown Newburgh, and the area was dubbed, "Upstate Broadway."

In the wake of World War II, the entertainment industry became dominated by motion pictures and television. Live theatrical performances dwindled, including opportunities for touring and vaudeville performers. As a result, employment opportunities for stagehands dwindled as well. The International discovered new growth opportunities in the construction of scenery for motion pictures and television, and began to expand into new territories. In order to keep theatrical scenery construction costs down, Broadway scene shops began moving upstate to Newburgh and later Cornwall in the 1970's. In 1978, Newburgh's Local 45 merged with Local 311. Local 637 of Kingston merged into 311 in 2000, and in 2019, Local 499 of Poughkeepsie was welcomed into 311's ranks as well.

Today, IATSE Local 311 serves the major theaters and scene shops of the Mid-Hudson Valley, including the 4,500-seat Eisenhower Hall at West Point Military Academy. 311 is well established as the driving force within PRG Scenic Technologies, crafting the Scenery and Automation for some of Broadway's best known hits, including Wicked, The Book of Mormon, Frozen, Dear Evan Hansen, and, of course, Phantom of the Opera. The talent, hard work and career commitments of the Brothers and Sisters of 311 are on display daily to Broadway visitors, and are shared globally on shows that tour the world.